Interplay between Charge, Orbital, and Magnetic Order in ${\mathrm{Pr}}_{1-\mathit{x}}{\mathrm{Ca}}_{\mathit{x}}{\mathrm{MnO}}_3$

We report resonant x-ray scattering studies of charge and orbital order in ${\mathrm{Pr}}_{1-x}{\mathrm{Ca}}_x{\mathrm{MnO}}_3$ with $x=0.4\mathrm{}$ and 0.5. Below the ordering temperature, $T_O=245\mathrm{}\mathrm{K}$, the charge and orbital order intensities follow the same temperature dependence, including an increase at the antiferromagnetic ordering temperature, $T_N$. High resolution measurements reveal, however, that long range orbital order is never achieved. Rather, an orbital domain state is formed. Above $T_O$, the charge order fluctuations are more highly correlated than the orbital fluctuations. We conclude that the charge order drives the orbital order at the transition.